Forward-backward study of the stereo vision problem

In stereo vision a pair of two-dimensional (2D) stereo images is given and the purpose is to find out the depth (disparity) of regions of the image in relation to the background, so that we can reconstruct the 3D structure of the image from the pair of 2D stereo images given. Using the Bayesian framework we implemented the Forward-Backward algorithm to unfold the disparity (depth) of a pair of stereo images. The results showed are very reasonable, but we point out there is room for improvement concerning the graph structure used.     

Friction stir weld-bonding defect inspection using phased array ultrasonic testing

Weight reduction is an important driver of the aerospace industry, which encourages the development of lightweight joining techniques to substitute rivet joints. Friction stir welding (FSW) is a solid-state process that enables the production of lighter joints with a small performance reduction compared to the base material properties. Increasing the FSW lap joint performance is an important concern. Friction stir weld bonding is a hybrid joining technology that combines FSW and adhesive bonding in order to increase the mechanical properties of FSW lap joints. FSW and hybrid lap joints were produced, using 2-mm-thick AA6082-T6 plates and a 0.2-mm-thick adhesive layer. Defect detection using the non-destructive test, phased array ultrasonic testing (PAUT), has been made. Microscopic observations were performed in order to validate the phased array ultrasonic testing results. Lap shear strength tests were carried out to quantify the joint’s quality. PAUT inspection successfully detected non-welded specimens but was not able to distinguish specimens with major hook defects from specimens correctly weld bonded with small hook defects.     

Synthesis and characterization of temperature‐responsive copolymers based on N‐vinylcaprolactam and their grafting on fibres

BACKGROUND: Responsive materials are able to respond reversibly to an environmental stimulus. When the stimulus is temperature in the physiological range, the responsive material is particularly interesting for textile applications. We describe here the synthesis and characterization of reactive temperature‐responsive copolymers and their subsequent grafting on cotton fabrics. RESULTS: Copolymers of N‐vinylcaprolactam and various reactive monomers were synthesized via free radical polymerization in solution. The copolymers were characterized in terms of chemical structure, molecular weight and temperature‐responsive properties. The copolymer of N‐vinylcaprolactam and methacrylic acid (11 or 22 wt%) and the hydrolysed copolymer of N‐vinylcaprolactam and acryloyl chloride were found to be temperature responsive. They were subsequently grafted on cotton fabrics. The grafting was studied using X‐ray photoelectron spectroscopy and scanning electron microscopy measurements and was found to be effective. Finally, the modified cotton fabrics were found to exhibit temperature‐responsive water regain and water vapour transmission rates. CONCLUSION: Temperature‐responsive copolymers were synthesized, characterized and successfully grafted on cotton fabrics, yielding responsive fabrics. Such fabrics can hence be used to modulate the skin microclimate under textiles. Copyright © 2009 Society of Chemical Industry     

Aluminum doped zinc oxide sputtering targets obtained from nanostructured powders: Processing and application

This work reports the production of ceramic targets based on nanostructured Al-doped ZnO (AZO) powders for sputtering applications. The nanostructured powder is obtained by a new patented process based on the detonation of an emulsion containing both Zn and Al metal precursors in the final proportion of 98:2 wt% (ZnO:Al₂O₃), through which the Al contains is highly uniform distributed over ZnO. Due to the nanostructured powder characteristics, the targets can be sintered at substantially lower temperatures (1150–1250 °C) by conventional sintering, contributing to production costs reduction of ceramic targets and consequently the costs of photovoltaic and displays industries. Electrical resistivity values around 3.0–7.0 × 10^?3 Ω cm have been obtained depending on final microstructure of the targets. The electro-optical properties of the films produced at room temperature with thicknesses around 360 nm, besides being highly uniform exhibit a resistivity of about 1 × 10^?3 Ω cm and a transmittance in the visible range above 90%.     

Maximum Power Point Tracking in a One-Cycle-Controlled Single-Stage Photovoltaic Inverter

In this paper, the design of the one-cycle controller of a single-stage inverter for photovoltaic applications is carried out by means of a multiobjective strategy to optimize inverter performance at both high and low insolation levels. Design constraints that account for different weather conditions are adopted. The optimization algorithm also provides useful information concerning the system sensitivity with respect to each of the controller parameters. This allows the design of a maximum power point tracking perturb and observe controller that significantly improves inverter performance. Experimental measurements confirm the predictions of theoretical and simulation results.     

Zinc oxide thin films: Characterization and potential applications

Zinc oxide (ZnO) has attracted recent interest for a range of applications, including use as a transparent conductive oxide (TCO) and in gas sensor devices. This paper compares ZnO films grown using two methods designed for the production of thin films, namely sol-gel and aerosol assisted chemical vapour deposition (AACVD) for potential use in sensor and TCO applications. Materials produced by the sol-gel route were observed to be amorphous when annealed at 350 °C, but were crystalline when annealed at higher temperatures and had a relatively open grain structure when compared to the AACVD films. Electrical characterization showed that materials were highly resistive, but that their properties varied considerably when the measurements were performed in vacuum or in air. This behaviour was rapidly reversible and reproducible for room temperature measurement.In contrast materials grown by aerosol-assisted CVD were non-porous, polycrystalline and conductive. Measured electrical properties did not vary with changing measurement atmosphere. These differences are discussed in terms of the structural characterisation of the films and some comments are made regarding the suitability of both approaches for the growth of ZnO thin film sensor materials.     

Oxide Semiconductor Thin‐Film Transistors: A Review of Recent Advances

Transparent electronics is today one of the most advanced topics for a wide range of device applications. The key components are wide bandgap semiconductors, where oxides of different origins play an important role, not only as passive component but also as active component, similar to what is observed in conventional semiconductors like silicon. Transparent electronics has gained special attention during the last few years and is today established as one of the most promising technologies for leading the next generation of flat panel display due to its excellent electronic performance. In this paper the recent progress in n‐ and p‐type oxide based thin‐film transistors (TFT) is reviewed, with special emphasis on solution‐processed and p‐type, and the major milestones already achieved with this emerging and very promising technology are summarizeed. After a short introduction where the main advantages of these semiconductors are presented, as well as the industry expectations, the beautiful history of TFTs is revisited, including the main landmarks in the last 80 years, finishing by referring to some papers that have played an important role in shaping transparent electronics. Then, an overview is presented of state of the art n‐type TFTs processed by physical vapour deposition methods, and finally one of the most exciting, promising, and low cost but powerful technologies is discussed: solution‐processed oxide TFTs. Moreover, a more detailed focus analysis will be given concerning p‐type oxide TFTs, mainly centred on two of the most promising semiconductor candidates: copper oxide and tin oxide. The most recent data related to the production of complementary metal oxide semiconductor (CMOS) devices based on n‐ and p‐type oxide TFT is also be presented. The last topic of this review is devoted to some emerging applications, finalizing with the main conclusions. Related work that originated at CENIMAT|I3N during the last six years is included in more detail, which has led to the fabrication of high performance n‐ and p‐type oxide transistors as well as the fabrication of CMOS devices with and on paper.